Successive Greek governments have deliberately adopted lax border controls in order to reap the benefits of exploitable labor, a new piece of research from the London School of Economics (LSE) has claimed.

A paper penned by assistant criminology professor Leonidas Cheliotis and released Wednesday suggests that over the past 25 years, Greek authorities have done little to reform ineffective migration policies in light of the economic and political benefits of keeping the status quo.

Cheliotis said that policies put forward by centrist parties like New Democracy and PASOK over the last two decades have maintained a high migrant population which has been crucial for filling low-prestige, poorly paid menial jobs, and holding up the shadow economy.

"Greek governments have engaged in the deliberate practice of allowing large waves of irregular migrants into the country in order to be able to exploit them once they're in, in order to satisfy the country's large informal labor market," he told CNBC in a phone interview.

Despite repeated claims to the contrary, the Greek state introduced policies and promoted practices that have kept the migrant population high by making piecemeal attempts at blocking irregular migration routes and failing to streamline processes like asylum claims, deportation or even voluntary repatriation programs, the paper explains.

Even with Greece viewed as a point of transit on the way to other European states, migrants have found themselves "trapped" by a system that relies on a highly-exploitable workforce, hemmed in by restrictive welfare and employment rights, and violent intimidation from the broader population, the report adds.

Eva Cosse, an assistant researcher with advocacy group Human Rights Watch, told CNBC that pressure on Greece to simultaneously take responsibility for both a disproportionate number of asylum seekers and for irregular migrants trying to enter EU borders "means that many asylum seekers find themselves trapped in what a 2008 Human Rights Watch report called 'a revolving door,'" she said.

"The failure of successive Greek governments to adopt coherent migration policies, chronic mismanagement of the asylum system, and, most recently, the deep economic crisis and resulting austerity have exacerbated what the United Nations High Commissioner for Refugees and others have described as a 'humanitarian crisis,'" she said.

The LSE report also claims that Alexis Tsipras' ruling Syriza party, which came to power in January 2015, may be prompting a shift just as the country faces unprecedented pressure from a ballooning migrant crisis.

Over 880,000 people illegally entered Greece in 2015, according to the EU border agency Frontex.

Cheliotis explained to CNBC that under Syriza, the legacy of deliberately exploitative migration policies has started to erode. While many of the realities on the ground have yet to change some of the harsh and discriminatory treatment of migrants and refugees landing on Greece's shores, Syriza has changed the tone of the national migrant debate.

But it may take longer to reverse reputational damages after migrants served as "scapegoats" for mainstream governments over the last two decades, he suggested, explaining there will still be difficulties in how outsiders are treated by the wider society.

The report comes on the heels of a tentative deal between the EU and Turkey to stem the flow of migrants to the bloc, with Ankara provisionally offering to take back migrants who enter Europe via their border.

The Greek Prime Minister's Office was not immediately available for comment when contacted by CNBC.